Retrospective cohort of 443 glioma patients analyzed under successive WHO classifications from 2007 to 2021.

Background: CNS tumors present significant diagnostic challenges due to their heterogeneity. Successive editions of the World Health Organization (WHO) classification have progressively incorporated molecular markers as essential criteria. Nonetheless, in low- and middle-income countries, limited access to molecular testing hampers the full application of these classifications. To assess this situation, we decided to evaluate the impact of successive WHO classifications on glioma diagnostic accuracy in a high-volume neurosurgical center in Latin America. We conducted a retrospective analysis of patients that underwent elective tumor surgery between January 1st, 2010 and December 31st, 2024 and whose pathology report was consistent with a glioma. Demographic, anatomical, histological, and molecular data were collected. Tumors were classified according to WHO CNS Tumor Classification criteria of 2007, 2016, and 2021. Statistical analyses were performed using STATA v15.A total of 443 patients were included. Under WHO 2007 criteria, glioblastoma was the most common tumor type, with virtually all tumors classified histologically. With WHO 2016 implementation, the proportion of tumors labeled as “not otherwise specified” (NOS) and cases with incomplete tumor characterization increased. Application of WHO 2021 further highlighted diagnostic limitations, with 24% of tumors categorized as high- or low-grade glioma NOS, instead of a particular tumor type/entity. This work sheds light on the fact that the progressive complexity of glioma classification with the addition of new molecular and genetic factors may have as a counterpart an increase in the number of cases with inadequate tumor characterization due to the lack of accessibility to key molecular studies in diagnosis.